1. Field of the Invention
This invention relates to a power receptacle with ground-fault circuit interrupter (GFCI) functions, and in particular, it relates to a disconnect mechanism in the power receptacle.
2. Description of the Related Art
When electrical appliances have a current leakage, abnormal current or voltage signals are generated. Leakage current protection devices can detect such abnormal current or voltage signals and used an operating mechanism to automatically cut off the power supply to the leaking appliances.
GFCI is a power receptacle that has a leakage current protection function. Their current limit is typically below 20 A and can detect leakage current of 6-30 mA. GFCIs are often used in handheld appliances, portable appliances, and are often used in homes, schools, etc.
A typical current type leakage current detection and protection devices includes a detection circuit (residual current detection), an intermediate mechanism (amplifier, comparator, or disconnecting mechanism), actuator and testing mechanism. A GFCI typically uses a disconnect mechanism as the intermediate mechanism.
Disconnect mechanisms can be categorized into electronic and electromagnetic types. Electromagnetic type disconnect mechanisms is widely used because it is more resistant to interference and shock (over current and over voltage), does not require auxiliary power supply, and does not change its protection functions at zero voltage.
Conventional GFCIs have certain shortcomings. For example, the GFCI described in Chinese patents ZL00250313.1 and ZL02243496.8, each moveable contact arm has one fixed end and another end with a contact terminal, so the connection and disconnection of the input and output ends of the receptacle relies on the resilient nature of the moving arms. However, the uniformity of the resilience of the moving arms is difficult to control during manufacturing, and cannot be tested using destructive test. Thus, if a moving arm is defective in its resilience, and if the load side experience an ultra-low ground fault (e.g. over 1000 A of leakage current), arcs may occur when the contact terminals are disconnected, which may melt the contact terminals and fuse them together. Thus, even though the disconnect mechanism of the GFCI is functional, the contact terminals are in fact not disconnected. This presents great hidden danger to safety.